缺少维度

Missing dimensions

我是 R 的新用户,我正在尝试使用面板数据(固定效应)来分析几个自变量对 GNI 对数的影响。我正在使用 plm 包,这是我的代码

library(plm)
head(project_data)

Y = cbind(project_data$log_GNI_PPP)
X = cbind(project_data$EU_application, project_data$EU_membership,
          project_data$distance_from_brussels, project_data$Former_USSR_DUMMY,
          project_data$natural_resources_pct,
          project_data$secondary_attendence_prct,
          project_data$eu_education_interaction)

project_data_panel = pdata.frame(project_data, index = c("country_name", "year"))
plm(Y ~ X, data = project_data_panel, model = "within")

但是,当我这样做时出现错误

Error in class(x) <- setdiff(class(x), "pseries") :
    invalid to set the class to matrix unless the dimension attribute is of length 2 (was 0)

我不确定这意味着什么,因为 X、Y 和 project_data_panel 似乎都分别具有正确的尺寸 (812 x 6) (812 x 1) 和 (812 x 16)。谁能看出我做错了什么?

这是数据示例

    dput(head(project_data, 50))
structure(list(country_name = c("Albania", "Albania", "Albania", 
"Albania", "Albania", "Albania", "Albania", "Albania", "Albania", 
"Albania", "Albania", "Albania", "Albania", "Albania", "Albania", 
"Albania", "Albania", "Albania", "Albania", "Albania", "Albania", 
"Albania", "Albania", "Albania", "Albania", "Albania", "Albania", 
"Albania", "Albania", "Armenia", "Armenia", "Armenia", "Armenia", 
"Armenia", "Armenia", "Armenia", "Armenia", "Armenia", "Armenia", 
"Armenia", "Armenia", "Armenia", "Armenia", "Armenia", "Armenia", 
"Armenia", "Armenia", "Armenia", "Armenia", "Armenia"), `Country Code` = c("ALB", 
"ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", 
"ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", 
"ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", "ALB", 
"ALB", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", 
"ARM", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", "ARM", 
"ARM", "ARM", "ARM", "ARM"), year = c(1990, 1991, 1992, 1993, 
1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 
2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 
2016, 2017, 2018, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 
1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 
2009, 2010), EU_application = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), EU_membership = c(0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0), distance_from_brussels = c(1589, 1589, 
1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 
1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 1589, 
1589, 1589, 1589, 1589, 1589, 3300, 3300, 3300, 3300, 3300, 3300, 
3300, 3300, 3300, 3300, 3300, 3300, 3300, 3300, 3300, 3300, 3300, 
3300, 3300, 3300, 3300), GNI_PPP_per_cap = c(2550, 1870, 1730, 
2120, 2310, 2710, 3050, 2780, 3110, 3550, 3980, 4460, 4800, 5150, 
5560, 5990, 6750, 7480, 8260, 8670, 9530, 10210, 10450, 10750, 
11360, 11800, 12060, 12960, 13350, 2340, 2240, 1130, 1190, 1430, 
1590, 1790, 1960, 2090, 2200, 2390, 2700, 3140, 3660, 4160, 4970, 
5870, 6970, 7700, 6590, 6890), GNI_PPP_GROWTH = c(NA, "-36.36%", 
"-8.09%", "18.40%", "8.23%", "14.76%", "11.15%", "-9.71%", "10.61%", 
"12.39%", "10.80%", "10.76%", "7.08%", "6.80%", "7.37%", "7.18%", 
"11.26%", "9.76%", "9.44%", "4.73%", "9.02%", "6.66%", "2.30%", 
"2.79%", "5.37%", "3.73%", "2.16%", "6.94%", "2.92%", NA, "-4.27%", 
"-49.55%", "5.31%", "20.17%", "11.19%", "12.58%", "9.50%", "6.63%", 
"5.26%", "8.64%", "12.97%", "16.30%", "16.56%", "13.66%", "19.47%", 
"18.11%", "18.74%", "10.47%", "-14.42%", "4.55%"), Stability_Index = c(NA, 
NA, NA, NA, NA, 8, 8, 9, 8, 7, 7, 7, 7, 7, 7, 5, 5, 4, 3, 3, 
3, 3, 2, 3, 2, 2, 2, 1, 1, NA, NA, NA, NA, NA, 8, 7, 8, 8, 8, 
8, 9, 7, 7, 7, 7, 7, 6, 6, 7, 7), Former_USSR_DUMMY = c(0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
1, 1, 1, 1, 1, 1), `Tertiary_enrollment rate` = c("8.3663600000000002", 
"8.8553300000000004", "9.2873199999999994", "11.17761", "10.63358", 
"10.202819999999999", "10.939450000000001", "12.699719999999999", 
"13.55017", "14.747769999999999", "15.53661", "15.904629999999999", 
"16.311430000000001", "16.657240000000002", "19.890440000000002", 
"23.189830000000001", "26.637139999999999", "30.68713", "32.092799999999997", 
"33.385550000000002", "44.549250000000001", "49.878700000000002", 
"59.252009999999999", "64.634429999999995", "65.782970000000006", 
"62.007620000000003", "58.38185", "57.375259999999997", "54.961329999999997", 
"23.204820000000002", "25.3567", "25.342120000000001", "23.027640000000002", 
"19.124310000000001", "19.082139999999999", "16.938569999999999", 
"22.720230000000001", "33.57358", "35.212409999999998", "35.549790000000002", 
"33.545299999999997", "36.146859999999997", "37.218879999999999", 
"37.883139999999997", "39.546770000000002", "43.115349999999999", 
"45.93094", "48.489330000000002", "51.334589999999999", "52.989150000000002"
), `Trade Openess` = c(39.4369634, 36.07052006, 108.7854722, 
80.51833277, 53.10258474, 47.61059487, 44.89542726, 45.42552335, 
48.13748354, 51.01107175, 63.4540744, 66.49104645, 68.52503792, 
67.02060851, 67.04722821, 70.87232827, 74.26708173, 83.20210079, 
77.45174863, 75.09481856, 76.54335524, 81.21856394, 76.51020102, 
75.87373278, 75.40786559, 71.80103037, 74.80985622, 78.16131198, 
77.08240186, 81.33571855, 100.8658552, 101.0767594, 107.9731463, 
112.4293646, 86.11485707, 79.22956012, 78.54774505, 71.84245188, 
70.56047914, 73.91851927, 71.61719663, 75.94344895, 82.18767117, 
75.03721018, 72.03895668, 62.60919306, 58.33644568, 55.70286492, 
58.47886987, 66.14730981), natural_resources_pct = c(11.05002975, 
9.344824468, 11.41790163, 2.804094484, 1.738143406, 1.28764727, 
1.334614417, 1.37003297, 0.304234074, 0.568541328, 1.094738792, 
0.732501135, 0.755764016, 0.762078498, 0.776381057, 1.050084705, 
1.431007073, 2.171629466, 1.629199242, 0.98009147, 2.033752543, 
3.455044143, 3.596119659, 3.578365186, 3.574896619, 1.813210471, 
1.049502751, 1.698859222, NA, 0, 0, 0.105584847, 0.102698623, 
0.468567478, 0.731881752, 0.511241769, 0.551497144, 0.160976758, 
0.141442386, 0.363203884, 0.29675514, 0.460041922, 0.520673274, 
0.974003626, 0.901240752, 1.788861711, 1.297061299, 1.294545673, 
1.656635559, 2.992128557), Tertiary_enrollment_rate_prop = c(0.0836636, 
0.0885533, 0.0928732, 0.1117761, 0.1063358, 0.1020282, 0.1093945, 
0.1269972, 0.1355017, 0.1474777, 0.1553661, 0.1590463, 0.1631143, 
0.1665724, 0.1989044, 0.2318983, 0.2663714, 0.3068713, 0.320928, 
0.3338555, 0.4454925, 0.498787, 0.5925201, 0.6463443, 0.6578297, 
0.6200762, 0.5838185, 0.5737526, 0.5496133, 0.2320482, 0.253567, 
0.2534212, 0.2302764, 0.1912431, 0.1908214, 0.1693857, 0.2272023, 
0.3357358, 0.3521241, 0.3554979, 0.335453, 0.3614686, 0.3721888, 
0.3788314, 0.3954677, 0.4311535, 0.4593094, 0.4848933, 0.5133459, 
0.5298915), log_GNI_PPP = c(7.84384863815247, 7.53369370984863, 
7.45587668749182, 7.65917136766606, 7.74500280351584, 7.90470391387375, 
8.02289686960146, 7.93020620668468, 8.04237800517328, 8.17470288246946, 
8.28903709827848, 8.40290404501411, 8.47637119689598, 8.54675199365778, 
8.62335338724463, 8.6978466911095, 8.81729778386658, 8.91998807096852, 
9.01917986651502, 9.06762406977459, 9.16219999664825, 9.23112291115871, 
9.25435725739296, 9.28266103355581, 9.33785369227514, 9.37585481045376, 
9.39764947028118, 9.46962296990626, 9.4992716638284, 7.75790620835175, 
7.71423114484909, 7.02997291170639, 7.08170858610557, 7.26542972325395, 
7.37148929521428, 7.4899708988348, 7.58069975222456, 7.64491934495886, 
7.69621263934641, 7.77904864492556, 7.90100705199242, 8.0519780789023, 
8.20521842639541, 8.33327035325531, 8.51117511909067, 8.67760991282214, 
8.84937050375457, 8.94897560784178, 8.79330862749655, 8.8378263640077
), secondary_attendence_prct = c(90.08174, 90.89363, 77.71476, 
70.33512, 68.72906, 68.67849, 67.86755, 69.36618, 71.31361, 71.54467, 
71.07808, 72.53716, 72.86855, 75.24344, 74.80221, 77.90939, 79.18955, 
82.20059, 84.12509, 85.69499, 88.10389, 89.79816, 92.28983, 96.25608, 
97.68487, 97.38848, 95.715, 95.26589, 95.43233, NA, 92.10371, 
92.32686, 94.7447, 96.62907, NA, 93.3364, 93.23616, 80.43603, 
80.05668, 92.15199, 88.28202, NA, NA, 89.34573, 92.05428, 94.94133, 
96.42764, 94.97048, 100.12562, 104.71332)), row.names = c(NA, 
50L), class = "data.frame")

这里只是用head

    head(project_data_panel, 50)
             country_name Country Code year EU_application EU_membership
Albania-1990      Albania          ALB 1990              0             0
Albania-1991      Albania          ALB 1991              0             0
Albania-1992      Albania          ALB 1992              0             0
Albania-1993      Albania          ALB 1993              0             0
Albania-1994      Albania          ALB 1994              0             0
Albania-1995      Albania          ALB 1995              0             0
Albania-1996      Albania          ALB 1996              0             0
Albania-1997      Albania          ALB 1997              0             0
Albania-1998      Albania          ALB 1998              0             0
Albania-1999      Albania          ALB 1999              0             0
Albania-2000      Albania          ALB 2000              0             0
Albania-2001      Albania          ALB 2001              0             0
Albania-2002      Albania          ALB 2002              0             0
Albania-2003      Albania          ALB 2003              0             0
Albania-2004      Albania          ALB 2004              0             0
Albania-2005      Albania          ALB 2005              0             0
Albania-2006      Albania          ALB 2006              0             0
Albania-2007      Albania          ALB 2007              0             0
Albania-2008      Albania          ALB 2008              0             0
Albania-2009      Albania          ALB 2009              1             0
Albania-2010      Albania          ALB 2010              1             0
Albania-2011      Albania          ALB 2011              1             0
Albania-2012      Albania          ALB 2012              1             0
Albania-2013      Albania          ALB 2013              1             0
Albania-2014      Albania          ALB 2014              1             0
Albania-2015      Albania          ALB 2015              1             0
Albania-2016      Albania          ALB 2016              1             0
Albania-2017      Albania          ALB 2017              1             0
Albania-2018      Albania          ALB 2018              1             0
Armenia-1990      Armenia          ARM 1990              0             0
Armenia-1991      Armenia          ARM 1991              0             0
Armenia-1992      Armenia          ARM 1992              0             0
Armenia-1993      Armenia          ARM 1993              0             0
Armenia-1994      Armenia          ARM 1994              0             0
Armenia-1995      Armenia          ARM 1995              0             0
Armenia-1996      Armenia          ARM 1996              0             0
Armenia-1997      Armenia          ARM 1997              0             0
Armenia-1998      Armenia          ARM 1998              0             0
Armenia-1999      Armenia          ARM 1999              0             0
Armenia-2000      Armenia          ARM 2000              0             0
Armenia-2001      Armenia          ARM 2001              0             0
Armenia-2002      Armenia          ARM 2002              0             0
Armenia-2003      Armenia          ARM 2003              0             0
Armenia-2004      Armenia          ARM 2004              0             0
Armenia-2005      Armenia          ARM 2005              0             0
Armenia-2006      Armenia          ARM 2006              0             0
Armenia-2007      Armenia          ARM 2007              0             0
Armenia-2008      Armenia          ARM 2008              0             0
Armenia-2009      Armenia          ARM 2009              0             0
Armenia-2010      Armenia          ARM 2010              0             0
             distance_from_brussels GNI_PPP_per_cap GNI_PPP_GROWTH Stability_Index
Albania-1990                   1589            2550           <NA>              NA
Albania-1991                   1589            1870        -36.36%              NA
Albania-1992                   1589            1730         -8.09%              NA
Albania-1993                   1589            2120         18.40%              NA
Albania-1994                   1589            2310          8.23%              NA
Albania-1995                   1589            2710         14.76%               8
Albania-1996                   1589            3050         11.15%               8
Albania-1997                   1589            2780         -9.71%               9
Albania-1998                   1589            3110         10.61%               8
Albania-1999                   1589            3550         12.39%               7
Albania-2000                   1589            3980         10.80%               7
Albania-2001                   1589            4460         10.76%               7
Albania-2002                   1589            4800          7.08%               7
Albania-2003                   1589            5150          6.80%               7
Albania-2004                   1589            5560          7.37%               7
Albania-2005                   1589            5990          7.18%               5
Albania-2006                   1589            6750         11.26%               5
Albania-2007                   1589            7480          9.76%               4
Albania-2008                   1589            8260          9.44%               3
Albania-2009                   1589            8670          4.73%               3
Albania-2010                   1589            9530          9.02%               3
Albania-2011                   1589           10210          6.66%               3
Albania-2012                   1589           10450          2.30%               2
Albania-2013                   1589           10750          2.79%               3
Albania-2014                   1589           11360          5.37%               2
Albania-2015                   1589           11800          3.73%               2
Albania-2016                   1589           12060          2.16%               2
Albania-2017                   1589           12960          6.94%               1
Albania-2018                   1589           13350          2.92%               1
Armenia-1990                   3300            2340           <NA>              NA
Armenia-1991                   3300            2240         -4.27%              NA
Armenia-1992                   3300            1130        -49.55%              NA
Armenia-1993                   3300            1190          5.31%              NA
Armenia-1994                   3300            1430         20.17%              NA
Armenia-1995                   3300            1590         11.19%               8
Armenia-1996                   3300            1790         12.58%               7
Armenia-1997                   3300            1960          9.50%               8
Armenia-1998                   3300            2090          6.63%               8
Armenia-1999                   3300            2200          5.26%               8
Armenia-2000                   3300            2390          8.64%               8
Armenia-2001                   3300            2700         12.97%               9
Armenia-2002                   3300            3140         16.30%               7
Armenia-2003                   3300            3660         16.56%               7
Armenia-2004                   3300            4160         13.66%               7
Armenia-2005                   3300            4970         19.47%               7
Armenia-2006                   3300            5870         18.11%               7
Armenia-2007                   3300            6970         18.74%               6
Armenia-2008                   3300            7700         10.47%               6
Armenia-2009                   3300            6590        -14.42%               7
Armenia-2010                   3300            6890          4.55%               7
             Former_USSR_DUMMY Tertiary_enrollment rate Trade Openess
Albania-1990                 0       8.3663600000000002      39.43696
Albania-1991                 0       8.8553300000000004      36.07052
Albania-1992                 0       9.2873199999999994     108.78547
Albania-1993                 0                 11.17761      80.51833
Albania-1994                 0                 10.63358      53.10258
Albania-1995                 0       10.202819999999999      47.61059
Albania-1996                 0       10.939450000000001      44.89543
Albania-1997                 0       12.699719999999999      45.42552
Albania-1998                 0                 13.55017      48.13748
Albania-1999                 0       14.747769999999999      51.01107
Albania-2000                 0                 15.53661      63.45407
Albania-2001                 0       15.904629999999999      66.49105
Albania-2002                 0       16.311430000000001      68.52504
Albania-2003                 0       16.657240000000002      67.02061
Albania-2004                 0       19.890440000000002      67.04723
Albania-2005                 0       23.189830000000001      70.87233
Albania-2006                 0       26.637139999999999      74.26708
Albania-2007                 0                 30.68713      83.20210
Albania-2008                 0       32.092799999999997      77.45175
Albania-2009                 0       33.385550000000002      75.09482
Albania-2010                 0       44.549250000000001      76.54336
Albania-2011                 0       49.878700000000002      81.21856
Albania-2012                 0       59.252009999999999      76.51020
Albania-2013                 0       64.634429999999995      75.87373
Albania-2014                 0       65.782970000000006      75.40787
Albania-2015                 0       62.007620000000003      71.80103
Albania-2016                 0                 58.38185      74.80986
Albania-2017                 0       57.375259999999997      78.16131
Albania-2018                 0       54.961329999999997      77.08240
Armenia-1990                 1       23.204820000000002      81.33572
Armenia-1991                 1                  25.3567     100.86586
Armenia-1992                 1       25.342120000000001     101.07676
Armenia-1993                 1       23.027640000000002     107.97315
Armenia-1994                 1       19.124310000000001     112.42936
Armenia-1995                 1       19.082139999999999      86.11486
Armenia-1996                 1       16.938569999999999      79.22956
Armenia-1997                 1       22.720230000000001      78.54775
Armenia-1998                 1                 33.57358      71.84245
Armenia-1999                 1       35.212409999999998      70.56048
Armenia-2000                 1       35.549790000000002      73.91852
Armenia-2001                 1       33.545299999999997      71.61720
Armenia-2002                 1       36.146859999999997      75.94345
Armenia-2003                 1       37.218879999999999      82.18767
Armenia-2004                 1       37.883139999999997      75.03721
Armenia-2005                 1       39.546770000000002      72.03896
Armenia-2006                 1       43.115349999999999      62.60919
Armenia-2007                 1                 45.93094      58.33645
Armenia-2008                 1       48.489330000000002      55.70286
Armenia-2009                 1       51.334589999999999      58.47887
Armenia-2010                 1       52.989150000000002      66.14731
             natural_resources_pct Tertiary_enrollment_rate_prop log_GNI_PPP
Albania-1990            11.0500298                     0.0836636    7.843849
Albania-1991             9.3448245                     0.0885533    7.533694
Albania-1992            11.4179016                     0.0928732    7.455877
Albania-1993             2.8040945                     0.1117761    7.659171
Albania-1994             1.7381434                     0.1063358    7.745003
Albania-1995             1.2876473                     0.1020282    7.904704
Albania-1996             1.3346144                     0.1093945    8.022897
Albania-1997             1.3700330                     0.1269972    7.930206
Albania-1998             0.3042341                     0.1355017    8.042378
Albania-1999             0.5685413                     0.1474777    8.174703
Albania-2000             1.0947388                     0.1553661    8.289037
Albania-2001             0.7325011                     0.1590463    8.402904
Albania-2002             0.7557640                     0.1631143    8.476371
Albania-2003             0.7620785                     0.1665724    8.546752
Albania-2004             0.7763811                     0.1989044    8.623353
Albania-2005             1.0500847                     0.2318983    8.697847
Albania-2006             1.4310071                     0.2663714    8.817298
Albania-2007             2.1716295                     0.3068713    8.919988
Albania-2008             1.6291992                     0.3209280    9.019180
Albania-2009             0.9800915                     0.3338555    9.067624
Albania-2010             2.0337525                     0.4454925    9.162200
Albania-2011             3.4550441                     0.4987870    9.231123
Albania-2012             3.5961197                     0.5925201    9.254357
Albania-2013             3.5783652                     0.6463443    9.282661
Albania-2014             3.5748966                     0.6578297    9.337854
Albania-2015             1.8132105                     0.6200762    9.375855
Albania-2016             1.0495028                     0.5838185    9.397649
Albania-2017             1.6988592                     0.5737526    9.469623
Albania-2018                    NA                     0.5496133    9.499272
Armenia-1990             0.0000000                     0.2320482    7.757906
Armenia-1991             0.0000000                     0.2535670    7.714231
Armenia-1992             0.1055848                     0.2534212    7.029973
Armenia-1993             0.1026986                     0.2302764    7.081709
Armenia-1994             0.4685675                     0.1912431    7.265430
Armenia-1995             0.7318818                     0.1908214    7.371489
Armenia-1996             0.5112418                     0.1693857    7.489971
Armenia-1997             0.5514971                     0.2272023    7.580700
Armenia-1998             0.1609768                     0.3357358    7.644919
Armenia-1999             0.1414424                     0.3521241    7.696213
Armenia-2000             0.3632039                     0.3554979    7.779049
Armenia-2001             0.2967551                     0.3354530    7.901007
Armenia-2002             0.4600419                     0.3614686    8.051978
Armenia-2003             0.5206733                     0.3721888    8.205218
Armenia-2004             0.9740036                     0.3788314    8.333270
Armenia-2005             0.9012408                     0.3954677    8.511175
Armenia-2006             1.7888617                     0.4311535    8.677610
Armenia-2007             1.2970613                     0.4593094    8.849371
Armenia-2008             1.2945457                     0.4848933    8.948976
Armenia-2009             1.6566356                     0.5133459    8.793309
Armenia-2010             2.9921286                     0.5298915    8.837826
             secondary_attendence_prct
Albania-1990                  90.08174
Albania-1991                  90.89363
Albania-1992                  77.71476
Albania-1993                  70.33512
Albania-1994                  68.72906
Albania-1995                  68.67849
Albania-1996                  67.86755
Albania-1997                  69.36618
Albania-1998                  71.31361
Albania-1999                  71.54467
Albania-2000                  71.07808
Albania-2001                  72.53716
Albania-2002                  72.86855
Albania-2003                  75.24344
Albania-2004                  74.80221
Albania-2005                  77.90939
Albania-2006                  79.18955
Albania-2007                  82.20059
Albania-2008                  84.12509
Albania-2009                  85.69499
Albania-2010                  88.10389
Albania-2011                  89.79816
Albania-2012                  92.28983
Albania-2013                  96.25608
Albania-2014                  97.68487
Albania-2015                  97.38848
Albania-2016                  95.71500
Albania-2017                  95.26589
Albania-2018                  95.43233
Armenia-1990                        NA
Armenia-1991                  92.10371
Armenia-1992                  92.32686
Armenia-1993                  94.74470
Armenia-1994                  96.62907
Armenia-1995                        NA
Armenia-1996                  93.33640
Armenia-1997                  93.23616
Armenia-1998                  80.43603
Armenia-1999                  80.05668
Armenia-2000                  92.15199
Armenia-2001                  88.28202
Armenia-2002                        NA
Armenia-2003                        NA
Armenia-2004                  89.34573
Armenia-2005                  92.05428
Armenia-2006                  94.94133
Armenia-2007                  96.42764
Armenia-2008                  94.97048
Armenia-2009                 100.12562
Armenia-2010                 104.71332

这是我的会话信息

R version 3.6.2 (2019-12-12)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363)

Matrix products: default

locale:
[1] LC_COLLATE=English_Ireland.1252  LC_CTYPE=English_Ireland.1252   
[3] LC_MONETARY=English_Ireland.1252 LC_NUMERIC=C                    
[5] LC_TIME=English_Ireland.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] plm_2.2-3

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.3       pillar_1.4.3     compiler_3.6.2   miscTools_0.6-26 bitops_1.0-6    
 [6] tools_3.6.2      testthat_2.3.1   digest_0.6.23    nlme_3.1-142     lattice_0.20-38 
[11] lifecycle_0.1.0  tibble_2.1.3     gtable_0.3.0     pkgconfig_2.0.3  rlang_0.4.5     
[16] bibtex_0.4.2.2   rstudioapi_0.10  maxLik_1.3-8     swirl_2.4.5      yaml_2.2.0      
[21] dplyr_0.8.4      httr_1.4.1       stringr_1.4.0    lmtest_0.9-37    gbRd_0.4-11     
[26] grid_3.6.2       tidyselect_1.0.0 glue_1.3.1       R6_2.4.1         bdsmatrix_1.3-4 
[31] Rdpack_0.11-1    Formula_1.2-3    ggplot2_3.2.1    purrr_0.3.3      magrittr_1.5    
[36] scales_1.1.0     MASS_7.3-51.4    assertthat_0.2.1 colorspace_1.4-1 sandwich_2.5-1  
[41] stringi_1.4.6    RCurl_1.98-1.1   lazyeval_0.2.2   munsell_0.5.0    crayon_1.3.4    
[46] zoo_1.8-7       
> 

plm() 期待 pdata.frame。您的来电

plm(Y ~ X, data = project_data_panel, model = "within")

将矩阵(Y 和 X)与 pdata.frame(project_data_panel)混合。正确的语法是

plm(log_GNI_PPP ~  EU_application + EU_membership + distance_from_brussels + Former_USSR_DUMMY + natural_resources_pct + secondary_attendence_prct + eu_education_interaction,  data = project_data_panel, model = "within")

您仍然需要检查 project_data_panel 是否具有所有必需的变量。您包含的数据中至少缺少名为 eu_education_interaction 的变量。